Samuel Mokrani / Mbed 2 deprecated USBAudio_micro

USBAudio example using a microphone

Dependencies:   USBDevice mbed

main.cpp@10:3eab670ff01f, 2013-03-01 (annotated)

Committer:
samux
Date:
Fri Mar 01 13:20:51 2013 +0000
Revision:
10:3eab670ff01f
Parent:
9:9de252a14cde 
use latest USBDevice lib (FRDM-KL25Z support)

Who changed what in which revision?

UserRevisionLine numberNew contents of line
samux 0:539ec61e1fbb 1 #include "mbed.h"
samux 8:caede7b4c444 2 #include "USBAudio.h"
samux 6:be128039be16 3
samux 5:b49b6a8ca111 4 // frequency: 8 kHz
samux 5:b49b6a8ca111 5 #define FREQ 8000
samux 5:b49b6a8ca111 6
samux 5:b49b6a8ca111 7 // 1 channel: mono
samux 5:b49b6a8ca111 8 #define NB_CHA 1
samux 0:539ec61e1fbb 9
samux 5:b49b6a8ca111 10 // length of an audio packet: each ms, we receive 48 * 16bits ->48 * 2 bytes. as there is one channel, the length will be 48 * 2 * 1
samux 5:b49b6a8ca111 11 #define AUDIO_LENGTH_PACKET (FREQ/500) * NB_CHA
samux 5:b49b6a8ca111 12
samux 9:9de252a14cde 13 // as we don't use audio in, 48000 and 1 are dummy
samux 10:3eab670ff01f 14 USBAudio audio(8000, 1, FREQ, NB_CHA, 0x0103, 0x4521);
samux 6:be128039be16 15
samux 3:e6a29c83ac52 16 AnalogIn mic(p20);
samux 0:539ec61e1fbb 17
samux 5:b49b6a8ca111 18 int16_t buf[AUDIO_LENGTH_PACKET/2];
samux 4:bef3b485f22e 19
samux 0:539ec61e1fbb 20 int main() {
samux 9:9de252a14cde 21 double mic_mean = 0.0;
samux 5:b49b6a8ca111 22 double mic_value;
samux 5:b49b6a8ca111 23
samux 5:b49b6a8ca111 24 // compute average value of the microphone. We can then center the audio signal sent to the computer
samux 5:b49b6a8ca111 25 for (int j = 0; j < 1000; j++) {
samux 5:b49b6a8ca111 26 mic_value = (mic.read_u16() >> 3);
samux 5:b49b6a8ca111 27 mic_mean = (mic_mean*j + mic_value)/(j+1);
samux 5:b49b6a8ca111 28 }
samux 3:e6a29c83ac52 29
samux 0:539ec61e1fbb 30 while (1) {
samux 5:b49b6a8ca111 31 for (int i = 0; i < AUDIO_LENGTH_PACKET/2; i++) {
samux 5:b49b6a8ca111 32 buf[i] = (mic.read_u16() >> 3) - mic_mean;
samux 5:b49b6a8ca111 33 if (i != AUDIO_LENGTH_PACKET/2) {
samux 6:be128039be16 34 wait_us(80);
samux 3:e6a29c83ac52 35 }
samux 3:e6a29c83ac52 36 }
samux 0:539ec61e1fbb 37 audio.write((uint8_t *)buf);
samux 9:9de252a14cde 38 }
samux 0:539ec61e1fbb 39 }